662 BILLEY LEVINSON 



Drug 



AET was selected as the chemoprotective agent because of its high degree 

 of effectiveness and its relatively low toxicity (DiStefano et al., 1956). It 

 has been shown that pretreatment of adult rats (Preston et al., 1959) and 

 mice (Doherty and Burnett, 1955; Urso et al., 1958) with AET reduces the 

 lethal effects of radiation, almost doubling the LD/50 from 700 r to 1,400 r. 



AET, 250 mg per kg of body weight, was administered intraperitoneally 

 10 minutes prior to irradiation. Adult rats tolerate a maximal dose of 294 

 mg per kg with no toxic effect (DiStephano, 1959; Doherty, 1959). A 

 somewhat lesser dose was selected because of considerations of increased 

 drug toxicity, later confirmed in fetal rats (Graham, 1960). 



The AET, dissolved in sterile saline just before injection, was prepared 

 in a concentration of 1.25% so that an 8 gm infant received 0.16 ml. Oozing 

 of the drug was prevented by inserting a 25 gauge needle approximately 

 0.5 cm subcutaneously before turning to enter the peritoneal cavity. If 

 damage to abdominal viscera was suspected, the animal was discarded. 



Behavioral Testing 



At 45 days of age, after 3 days of preliminary adaptation in a single unit 

 straight-alley Lashley I maze, the rats were introduced into the Lashley III 

 maze (Lashley, 1929). They were then given five trials per day until they 

 reached a learning criterion of two out of three consecutive errorless trials 

 completed within 10 seconds. An error was defined as entrance into a blind 

 alley by a full body length or as the retracing of one maze unit. The time per 

 trial was measured from the time the animal left the "start" box until it 

 reached the food. 



Thirty days after reaching the criterion in the acquisition series, the 

 surviving animals were again placed in the Lashley III maze and given 

 five trials per day until they regained the criterion. These scores constituted 

 the retention scores. 



Throughout the testing, the rats were maintained on a 23 hour depriva- 

 tion schedule. A 24 hour feeding rhythm was established two days before 

 each testing period. The food incentive was Purina laboratory chow, mois- 

 tened and made into pellets. 



Results 



Mortality 



The mortality data appear in Table I, including the number of rats which 

 received each neonatal treatment and the percentage of 45 day and 75 day 



